Film-Tech Forum ARCHIVE: Either 'scope 35mm isn't 4k or IMAX study wrong

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Posted by Lyle Romer (Member # 1266) on 07-30-2012, 09:12 AM:

I remember reading something a few years ago that IMAX did a study where they put a checkerboard of increasing resolution on IMAX film and the result was that beyond 4k nobody could decern pixels except the very closest to the screen.

The other psuedo fact regarding the digital cinema debate is that 4k digital is still not good enough to replace 4k scope 35mm.

Having seen Dark Knight Rises in IMAX from the 2nd to back row, there was a clear (pun intended) difference in quality and resolution (not just picture height) between the scenes filmed in IMAX and the scenes filmed in 35mm. Assuming they used the same process as with The Dark Knight where the 35mm was scanned at 8k for printing to the IMAX version, something doesn't add up. Either humans are more than capable of discerning resolution beyond 4k or 35mm doesn't capture anything near 4k because those scenes while not looking terrible were nowhere near as sharp as the IMAX scenes.

Posted by Randy Stankey (Member # 64) on 07-30-2012, 11:25 AM:

I think it's more than just resolution.

You have to consider contrast ratios or dynamic range. You have to consider color resolution/depth. There's chromatic abberation and, finally, you need to consider the differences in the way the human brain perceives an image made up of pixels arranged in Cartesian fashion versus randomly oriented grains of silver or rosettes of color.

To me, a well presented film gives the impression of an image that has depth beyond the screen where a digital image looks like is is just painted on the surface.

As far as I am concerned, most people who claim that digital video is as good as or better are only comparing a mediocre film presentation to a well done digital presentation and they don't take into account the fundamental differences between the technologies.

In terms of daily operating cost, convenience and flexibility, digital comes out on top but, in terms of picture quality, I don't think it can ever beat film.

People who say that digital video beats a well done film presentation based solely in terms of pixel resolution just aren't considering all the factors.

Posted by Monte L Fullmer (Member # 2797) on 07-30-2012, 01:22 PM:

4K is close to a 1.85/1 flat image presentation.

Using 'scope in the equation isn't the best since you're comparing a distorted image against a normal image .. which, in a way is reducing resolution.

Apples and Oranges here, once again.

Posted by Rick Raskin (Member # 1561) on 07-30-2012, 04:20 PM:

quote: Randy Stankey
...you need to consider the differences in the way the human brain perceives an image made up of pixels arranged in Cartesian fashion versus randomly oriented grains of silver or rosettes of color.

Well said!

Posted by Jeffry L. Johnson (Member # 453) on 08-03-2012, 10:33 AM:

According to an IMAX authored 1993 SMPTE pre-print article, 40 line pairs per millimeter resolvable information on screen means the area of an IMAX frame is 5568 x 3880 viewable pixels. A 35mm frame is 1608 x 1216 viewable pixels.

quote:
Preprint No. 135-22
IMAX HD -- A HIGH DEFINITION MOTION PICTURE SYSTEM

Paul Panabaker, Albert Darimont, Michael Gibbon, Ian Maxwell, and William Shaw
Imax Corporation
Mississauga, Ont., Canada

presented at the
135th SMPTE Technical Conference
October 29 - November 2, 1993
Los Angeles Convention Center, Los Angeles, Calif.

Appendix 1 - Information Content of Various Display Formats

Format: NTSC
Film Dimensions:
H (mm):
V (mm):
Area (mm^2):
Film Negative Pixels (a):
H: 437
V: 483
Total Pixels (HxV): 0.2 M
Viewable Pixels (b):
H: 350
V: 338
Total Pixels (HxV): 0.1 M
Field/Frame (rate/sec): 30
Bandwidth (Mbytes/sec)(c): 11
Percentage of IMAX HD: 0.3 %

Format: HDTV
Film Dimensions:
H (mm):
V (mm):
Area (mm^2):
Film Negative Pixels (a):
H: 1030
V: 1035
Total Pixels (HxV): 1.1 M
Viewable Pixels (b):
H: 1030
V: 686
Total Pixels (HxV): 0.7 M
Field/Frame (rate/sec): 30
Bandwidth (Mbytes/sec)(c): 64
Percentage of IMAX HD: 2.0 %

Format: 35 mm / 4 perf
Film Dimensions:
H (mm): 20.1
V (mm): 15.2
Area (mm^2): 306
Film Negative Pixels (a):
H: 3216
V: 2432
Total Pixels (HxV): 7.8 M
Viewable Pixels (b):
H: 1608
V: 1216
Total Pixels (HxV): 2.0 M
Field/Frame (rate/sec): 24
Bandwidth (Mbytes/sec)(c): 141
Percentage of IMAX HD: 4.5 %

Format: 70 mm / 5 perf
Film Dimensions:
H (mm): 48.6
V (mm): 22.1
Area (mm^2): 1074
Film Negative Pixels (a):
H: 7776
V: 3536
Total Pixels (HxV): 27.5 M
Viewable Pixels (b):
H: 3888
V: 1768
Total Pixels (HxV): 6.9 M
Field/Frame (rate/sec): 60
Bandwidth (Mbytes/sec)(c): 1237
Percentage of IMAX HD: 39.8 %

Format: 70 mm / 8 perf
Film Dimensions:
H (mm): 48.6
V (mm): 36.3
Area (mm^2): 1764
Film Negative Pixels (a):
H: 7776
V: 5808
Total Pixels (HxV): 45.2 M
Viewable Pixels (b):
H: 3888
V: 2904
Total Pixels (HxV): 11.3 M
Field/Frame (rate/sec): 24
Bandwidth (Mbytes/sec)(c): 813
Percentage of IMAX HD: 26.1 %

Format: 70 mm / 8 perf
Film Dimensions:
H (mm): 48.6
V (mm): 36.3
Area (mm^2): 1764
Film Negative Pixels (a):
H: 7776
V: 5808
Total Pixels (HxV): 45.2 M
Viewable Pixels (b):
H: 3888
V: 2904
Total Pixels (HxV): 11.3 M
Field/Frame (rate/sec): 30
Bandwidth (Mbytes/sec)(c): 1016
Percentage of IMAX HD: 32.7 %

Format: 70 mm / 15 perf IMAX
Film Dimensions:
H (mm): 69.6
V (mm): 48.5
Area (mm^2): 3376
Film Negative Pixels (a):
H: 11136
V: 7760
Total Pixels (HxV): 86.4 M
Viewable Pixels (b):
H: 5568
V: 3880
Total Pixels (HxV): 21.6 M
Field/Frame (rate/sec): 24
Bandwidth (Mbytes/sec)(c): 1555
Percentage of IMAX HD: 50.0 %

Format: 70 mm / 15 perf IMAX HD
Film Dimensions:
H (mm): 69.6
V (mm): 48.5
Area (mm^2): 3376
Film Negative Pixels (a):
H: 11136
V: 7760
Total Pixels (HxV): 86.4 M
Viewable Pixels (b):
H: 5568
V: 3880
Total Pixels (HxV): 21.6 M
Field/Frame (rate/sec): 48
Bandwidth (Mbytes/sec)(c): 3111
Percentage of IMAX HD: 100 %

Notes:
a) assuming 80 lp/mm resolvable information on film negative; video data from: Carlson, SMPTE Journal Dec. 1984
b) assuming 40 lp/mm resolvable information on screen; video data from: Carlson, SMPTE Journal Dec. 1984, HDTV is NHK std.
c) bandwidth = (total viewable pixels x frame rate x 24 colour bits/pixel) / 8 bits/byte

Posted by Manny Knowles (Member # 1171) on 08-03-2012, 12:45 PM:

I would question any IMAX study that concludes that IMAX is best.

Not saying it's not true. But my first instinct is to "consider the source" and note that they clearly have an agenda.

Posted by Steve Guttag (Member # 268) on 08-03-2012, 06:13 PM:

Negative resolution is notably above 80 lines/mm considering NTAV's "RP40" target has line pairs above that (100...as I recall and our projectors have no problem resolving that!).

Posted by Louis Bornwasser (Member # 3063) on 08-06-2012, 12:54 PM:

All test film are the weak link on a top quality projection system. Louis